The 17-year-old attempted to rob mobile phones and money from Gadgetz Exchange on April 27.
The boy, who cannot be identified due to his age, was arrested and charged with attempted robbery and possession of an imitation firearm whilst committing an offence.
He pleaded guilty to both charges on April 30 and will be sentenced at Bromley Magistrates’ Court in June.
The teen was released on bail with an electronic tag and a ban on entering Bromley High Street.
